/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.runners.core;



import com.bff.gaia.unified.sdk.state.State;

import com.bff.gaia.unified.sdk.state.StateContext;

import com.bff.gaia.unified.vendor.guava.com.google.common.base.Equivalence;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.HashBasedTable;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.Table;



import javax.annotation.Nullable;

import java.util.HashMap;

import java.util.Map;

import java.util.Set;



/**

 * Table mapping {@code StateNamespace} and {@code StateTag<?>} to a {@code State} instance.

 *

 * <p>Two {@link StateTag StateTags} with the same ID are considered equivalent. The remaining

 * information carried by the {@link StateTag} is used to configure an empty state cell if it is not

 * yet initialized.

 */

public abstract class StateTable {



  private final Table<StateNamespace, Equivalence.Wrapper<StateTag>, State> stateTable =

      HashBasedTable.create();



  /**

   * Gets the {@link State} in the specified {@link StateNamespace} with the specified {@link

   * StateTag}, binding it using the {@link #binderForNamespace} if it is not already present in

   * this {@link StateTable}.

   */

  public <StateT extends State> StateT get(

	  StateNamespace namespace, StateTag<StateT> tag, StateContext<?> c) {



    Equivalence.Wrapper<StateTag> tagById = StateTags.ID_EQUIVALENCE.wrap((StateTag) tag);



    @Nullable State storage = getOrNull(namespace, tagById, c);

    if (storage != null) {

      @SuppressWarnings("unchecked")

      StateT typedStorage = (StateT) storage;

      return typedStorage;

    }



    StateT typedStorage = tag.bind(binderForNamespace(namespace, c));

    stateTable.put(namespace, tagById, typedStorage);

    return typedStorage;

  }



  /**

   * Gets the {@link State} in the specified {@link StateNamespace} with the specified identifier or

   * {@code null} if it is not yet present.

   */

  @Nullable

  public State getOrNull(

	  StateNamespace namespace, Equivalence.Wrapper<StateTag> tag, StateContext<?> c) {

    return stateTable.get(namespace, tag);

  }



  public void clearNamespace(StateNamespace namespace) {

    stateTable.rowKeySet().remove(namespace);

  }



  public void clear() {

    stateTable.clear();

  }



  public Iterable<State> values() {

    return stateTable.values();

  }



  public boolean isNamespaceInUse(StateNamespace namespace) {

    return stateTable.containsRow(namespace);

  }



  public Map<StateTag, State> getTagsInUse(StateNamespace namespace) {

    // Because of shading, Equivalence.Wrapper cannot be on the API surface; it won't work.

    // If runners-core ceases to shade Guava then it can (all runners should shade runners-core

    // anyhow)

    Map<Equivalence.Wrapper<StateTag>, State> row = stateTable.row(namespace);

    HashMap<StateTag, State> result = new HashMap<>();



    for (Map.Entry<Equivalence.Wrapper<StateTag>, State> entry : row.entrySet()) {

      result.put(entry.getKey().get(), entry.getValue());

    }



    return result;

  }



  public Set<StateNamespace> getNamespacesInUse() {

    return stateTable.rowKeySet();

  }



  /**

   * Provide the {@code StateBinder} to use for creating {@code Storage} instances in the specified

   * {@code namespace}.

   */

  protected abstract StateTag.StateBinder binderForNamespace(StateNamespace namespace, StateContext<?> c);

}